High voltage comparator with low-sensitivity to variations of process/temperature and supply

Abstract

A voltage comparator for detecting a voltage difference in a high-voltage domain, wherein said comparator receives an input voltage and compares it with a reference voltage also received in input, in which the output voltage from the comparator assumes the logic value 1 if the input voltage is greater than the reference voltage and assumes the logic value 0 if the input voltage is less than or equal to the reference voltage, wherein said comparator comprises low-voltage components and a single high-voltage component. In particular, the low-voltage components are MOS transistors and the high-voltage component is a high-voltage PMOS.

The invention claimed is: 
     
       1. A voltage comparator, comprising:
 a first input terminal configured to receive a first input voltage; 
 a second input terminal configured to receive a second input voltage; 
 a reference terminal configured to receive a reference voltage; 
 a first transistor having a control terminal electrically coupled to the first input terminal and a first conduction terminal electrically coupled to the second input terminal, the first transistor being configured to be controlled by the first input voltage and provide a first current that is proportional to a voltage difference between the first and second input voltages; 
 a second transistor having a first conduction terminal coupled to the reference terminal and configured to provide a second current that is proportional to the reference voltage; 
 a first current mirror coupled between the first and second transistors and configured to provide a third current that is proportional to the first current and 
 an output terminal configured to receive the second and third currents and provide the output voltage based on a comparison of the second and third currents. 
 
     
     
       2. The voltage comparator of  claim 1 ,
 wherein the output terminal of the voltage comparator outputs a logic high value when the second current is larger than the third current, and outputs a logic low value when the second current is smaller than the third current. 
 
     
     
       3. The voltage comparator of  claim 2 , further comprising:
 a third transistor electrically coupled between the first and second input terminals and configured to provide a fourth current; 
 a fourth transistor coupled in series with the first transistor and forming a second current mirror with the third transistor; and 
 a first resistor coupled in series with the third transistor between the first and second input terminals. 
 
     
     
       4. The voltage comparator of  claim 3 , further comprising:
 a fifth transistor forming a third current mirror with the second transistor; and 
 a second resistor coupled in series with the fifth transistor between the reference voltage terminal and a ground terminal. 
 
     
     
       5. The voltage comparator of  claim 4 , wherein the first current mirror includes:
 a sixth transistor electrically coupled in series with the second transistor between the reference terminal and the ground terminal; and 
 a seventh transistor coupled in series with the first and fourth transistors and having a control terminal directly connected to a control terminal of the sixth transistor. 
 
     
     
       6. The voltage comparator of  claim 5 , wherein:
 the first and second resistors have substantially equal resistances and the first, second, and third current mirrors have respective mirror ratios that are configured to ensure that the fourth current, through the first resistor and third transistor, substantially equals a fifth current through the second resistor and fifth transistor. 
 
     
     
       7. The voltage comparator of  claim 5 , wherein the first transistor is a high-voltage transistor and the second, third, fourth, fifth, sixth, and seventh transistors are low-voltage transistors. 
     
     
       8. A DC-DC converter controller, comprising:
 a power switch element configured to provide an output drive voltage; and 
 a comparator that includes:
 a first input terminal configured to receive the output drive voltage from the power switch element as a first input voltage; 
 a second input terminal configured to receive a second input voltage; 
 a reference terminal configured to receive a reference voltage; 
 a first transistor having a control terminal electrically coupled to the first input terminal and a first conduction terminal electrically coupled to the second input terminal, the first transistor being configured to be controlled by the first input voltage and provide a first current that is proportional to a voltage difference between the first and second input voltages; 
 a second transistor having a first conduction terminal coupled to the reference terminal and configured to provide a second current that is proportional to the reference voltage; 
 a first current mirror coupled between the first and second transistors and configured to provide a third current that is proportional to the first current; and 
 an output terminal configured to receive the second and third currents and provide the output voltage based on a comparison of the second and third currents. 
 
 
     
     
       9. The DC-DC converter controller of  claim 8 , wherein the output terminal of the comparator outputs a logic high value when the second current is larger than the third current, and outputs a logic low value when the second current is smaller than the third current. 
     
     
       10. The DC-DC converter controller of  claim 9 , wherein the comparator includes:
 a third transistor electrically coupled between the first and second input terminals and configured to provide a fourth current; 
 a fourth transistor coupled in series with the first transistor and forming a second current mirror with the third transistor; and 
 a first resistor coupled in series with the third transistor between the first and second input terminals. 
 
     
     
       11. The DC-DC converter controller of  claim 10 , wherein the comparator includes:
 a fifth transistor forming a third current mirror with the second transistor; and 
 a second resistor coupled in series with the fifth transistor between the reference voltage terminal and a ground terminal. 
 
     
     
       12. The DC-DC converter controller of  claim 11 , wherein the first current mirror includes:
 a sixth transistor electrically coupled in series with the second transistor between the reference terminal and the ground terminal; and 
 a seventh transistor coupled in series with the first and fourth transistors and having a control terminal directly connected to a control terminal of the sixth transistor. 
 
     
     
       13. The DC-DC converter controller of  claim 12 , wherein:
 the first and second resistors have substantially equal resistances and the first, second, and third current mirrors have respective mirror ratios that are configured to ensure that the fourth current, through the first resistor and third transistor, substantially equals a fifth current through the second resistor and fifth transistor. 
 
     
     
       14. The DC-DC converter controller of  claim 8 , further comprising:
 a switch driver configured to control the switch element and receive power from the second input voltage; and 
 a control logic circuit configured to control the switch driver based in part on the output voltage provided by the comparator. 
 
     
     
       15. A DC-DC converter, comprising:
 a bootstrap capacitor; and 
 a DC-DC converter controller that includes:
 a power switch element configured to provide an output drive voltage for driving the inverter circuit; and 
 a comparator that includes:
 a first input terminal configured to receive the output drive voltage from the power switch element as a first input voltage; 
 a second input terminal configured to receive a second input voltage from the bootstrap capacitor, the bootstrap capacitor being connected to the first and second input terminal; 
 a reference terminal configured to receive a reference voltage; 
 a first transistor having a control terminal electrically coupled to the first input terminal and a first conduction terminal electrically coupled to the second input terminal, the first transistor being configured to be controlled by the first input voltage and provide a first current that is proportional to a voltage difference between the first and second input voltages; 
 a second transistor having a first conduction terminal coupled to the reference terminal and configured to provide a second current that is proportional to the reference voltage; 
 a first current mirror coupled between the first and second transistors and configured to provide a third current that is proportional to the first current; and 
 an output terminal configured to receive the second and third currents and provide the output voltage based on a comparison of the second and third currents. 
 
 
 
     
     
       16. The DC-DC converter of  claim 15 , wherein the output terminal of the comparator of the DC-DC converter controller outputs a logic high value when the second current is larger than the third current, and outputs a logic low value when the second current is smaller than the third current. 
     
     
       17. The DC-DC converter of  claim 16 , wherein the comparator includes:
 a third transistor electrically coupled between the first and second input terminals and configured to provide a fourth current; 
 a fourth transistor coupled in series with the first transistor and forming a second current mirror with the third transistor; and 
 a first resistor coupled in series with the third transistor between the first and second input terminals. 
 
     
     
       18. The DC-DC converter of  claim 17 , wherein the comparator includes:
 a fifth transistor forming a third current mirror with the second transistor; and 
 a second resistor coupled in series with the fifth transistor between the reference voltage terminal and a ground terminal. 
 
     
     
       19. The DC-DC converter of  claim 18 , wherein the first current mirror includes:
 a sixth transistor electrically coupled in series with the second transistor between the reference terminal and the ground terminal; and 
 a seventh transistor coupled in series with the first and fourth transistors and having a control terminal directly connected to a control terminal of the sixth transistor. 
 
     
     
       20. The DC-DC converter of  claim 19 , wherein:
 the first and second resistors have substantially equal resistances and the first, second, and third current mirrors have respective mirror ratios that are configured to ensure that the fourth current, through the first resistor and third transistor, substantially equals a fifth current through the second resistor and fifth transistor.